Zero degrees azimuth is usually set toward a heading of true north.

通常将正北朝向方位角度记为0度方位角。

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Then the azimuth of formation fractures is estimated; and with the joint use of zero offset P wave source VSP data, fast and slow shear wave seismograms are obtained to have fracture density.

在获得地下裂隙方位角的同时，结合零偏纵波VSP资料得到快、慢S波记录，进而计算了裂隙密度。

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